1. Field of the Invention
This invention relates to an air suspension control system for a vehicle such as an ambulance, bus, semi-truck, rescue vehicle, pick-up truck or automobile. More particularly, this invention relates to an air suspension control system which includes a lift mechanism which may be used to maintain the vehicle at a ride height position and to cause the lift mechanism to be moved to a kneeling position. Even more particularly, this invention relates to a system whereby the kneeling process may be halted at any time before the kneeling process is completed through the use of a single switch.
2. Description of the Related Art
Conventional air suspension systems have long been on vehicles such as automobiles, trucks, buses, and emergency vehicles such as ambulances. The prior art air suspension systems normally utilize air springs which are positioned between the vehicle axles and the vehicle chassis. The prior art air suspension systems are also adapted to control the height of the vehicle when the vehicle is carrying loads of various weights. Further, the air suspension systems of the prior art are capable of leveling the vehicle when the vehicle is resting on uneven surfaces.
The prior art air suspensions are also utilized on public buses and emergency vehicles, with the air suspension systems thereof being capable of lowering portions of the vehicle, usually the rear end thereof or one side thereof for selected periods of time which is normally referred to “kneeling”. For example, the passenger entrance/exit side of a public bus may be lowered or kneeled to lower that side of the bus to enable persons to more easily enter the bus or exit the bus.
In emergency vehicles, such as ambulances, the rear end of the emergency vehicle is lowered or kneeled to enable a stretcher or the like to be more easily placed within the ambulance and to be removed therefrom. U.S. Pat. No. 8,413,997 issued on Apr. 9, 2013 which solved many of the problems associated with the kneeling of vehicles. However, the system of U.S. Pat. No. 8,413,997 has certain shortcomings or drawbacks as will now be described.
In the system of U.S. Pat. No. 8,413,997, when the suspension system is in the kneeling process and has not reached its kneel height setting, the suspension system cannot recover or return to its ride height unless the two kneel input signals are activated which usually involves the closure of the rear door(s) of the ambulance and the depression of the brake pedal in the cab of the ambulance thereby causing the suspension to recover to the design height setting. This means that once the suspension system of U.S. Pat. No. 8,413,997 starts kneeling, it will always go all the way down, unless a person is quick enough to both close the rear door and press the brake pedal before it finishes kneeling. This shortcoming is critical should someone be underneath the vehicle during maintenance or repair work.
Further, the suspension system of U.S. Pat. No. 8,413,997 may be activated into its kneeling mode if the transmission of the vehicle is not in the park position. There may be some disadvantage or problem with incorporating such a transmission park feature but Applicant's system of this invention eliminates those potential disadvantages or problems.